1. Field of the Invention
This invention relates to a rotary brush, and particularly to a rotary brush for a cleaner having at least one flexible blade extending perpendicularly with respect to the axis or rotation thereof and operates to sweep up dust as a result of abutting of the blade upon a surface to be cleaned.
2. Description of the Related Art
Heretofore, a bristle type rotary brush wherein bristles are fixed around a rotating basic shaft has been used as a rotary brush for cleaners. There has been, however, such a problem that bristles are wound or twined with pieces of thread, cotton and the like (hereinafter referred to simply as "waste threads"). In order to solve the problem, the present applicant has proposed a rotary brush of a blade type by which winding or twining of waste threads is prevented and which is disclosed in Japanese Patent Publication No. 35246/1988. This rotary brush described in Patent Publication No. 35246/1988 is constructed in such a way that the surface of the rotating basic shaft has at least one flexible blade extending perpendicularly with respect to the axis of rotation thereof, the extreme edge portion of a blade, i.e. the portion standing face to face with a surface to be cleaned being provided with innumerable minute projections. These projections are for improving capability of collecting minute dust particles. For the sake of satisfying a requirement of flexibility and wear resistance in a material to be used, vulcanized rubber (hereinafter referred to simply as "rubber") has been used.
However, although such blades as described above have no problem in the case where they are used in a low speed rotation zone (around 1000 rpm) for a manual cleaner, there have been the following three problems in a high speed rotation zone (3000-6000 rpm) as in a vacuum cleaner. Namely, they are:
(1) Wearing of the blades is remarkable.
Particularly, the innumerable minute projections provided for improving capability of collecting minute dust wear easily so that capability of collecting dust becomes inferior. The present applicant has made various experiments in respect of respective brands of rubber and thermoplastic elastomeric materials. As a result, even a material having the highest wear resistance exhibits such life being half or less than that of the rotary brush of a bristle type, besides the cost therefor is several times higher than that of conventional blades. Thus, results of the experiment were quite unsatisfactory.
(2) Pile yarn in a loop carpet is damaged.
Since rubber has generally high wear resistance, such rubber functions so as to comb the pile yarn of a carpet in the case where the carpet is rubbed with a rotary brush of rubber blade type. As a result, there appears fuzzing of the pile yarn which damages feeling of the carpet.
(3) As a result of cleaning by the use of the rotary brush described above, a floor surface is stained black by rubbing the same with the blades.
This is because carbon black which has been incorporated in rubber for elevating various physical properties transfers to the floor surface as a result of rubbing the same with the blades of the above described rotary brush.